1. Technical Field
The present invention generally relates to a method of fabricating a plurality of pipes for conveying fluid, for example those adapted for use in a gasoline tank of an automobile, and particularly to a method of fabricating a resin-made bundle-like pipe unit including a plurality of independent pipes joined with each other at the lateral walls thereof, as well as to the pipe units produced thereby.
2. Background Art
Generally, a pipe unit used as an inlet pipe of a gasoline tank of an automobile includes a large bore pipe (called "parent pipe") for conveying the gasoline and a small bore pipe (called "child pipe") for breathing. Usually, the child pipe is coupled with the parent pipe at one end thereof, and these two pipes define a single pipe unit.
Conventionally, the above-mentioned pipe units are made of metal and manufactured by joining the child pipe with the parent pipe by means of brazing or spot welding at a part thereof and coupling the child pipe with the parent pipe at one end thereof. However, this method has the following shortcomings:
(1) The pipe unit is heavy in weight since each pipe is made from metal. PA1 (2) Many steps are required in manufacturing the pipe unit so that it is difficult to lower the product cost. PA1 (3) The pipes are subject to rusting since they are metallic. PA1 (4) When one end of the child pipe is coupled with the parent pipe, problems are inevitable since the metallic pipes do not possess flexibility.
On the other hand, it also known that two resin pipes can be separately manufactured by means of blow molding and then joined with each other. One of the blow molding methods of fabricating the pipes is disclosed in Japanese patent application Second Publication No. 58-47337 (47337/1983). In this reference, parison is supplied from the molding machine and introduced into a hollow having a predetermined configuration made in the molding die, then air is blown in the parison so as to inflate the parison. Accordingly, a single pipe is provided by blow molding which has a configuration which conforms to the hollow formed in the molding die. However, in order to obtain a bundle-like pipe unit having a plurality of independent pipes by this method, the plurality of pipes have to be molded separately and then joined with each other.